Currently my MailEnable SMTP server is enabled and when I look at the log files of the SMTP server, I see lots and lots of entries with my domain name. I think most of the entries are the records of abusive SMTP server connection tries - someone trying to use my SMTP server with my domain name to send out JUNK email messages.

I NEVER created mail box with the name wikiuser for my domain name. And just by looking at today's SMTP log file, I see hundreds (if not thousands) of these entries with the guessed mail box names such as wikiuser, sonya, sophie, wil etc.
It looks like the IP address 92.118.38.57 has been reported 2704 times according to the information shown at abuseip.com and it's in London, UK.
Why is this happening? Is it because someone's trying to send junk mail using my domain name?

I don't know who's doing this but I have questions:

Q: Is this normal? Do most mailenable SMTP servers installed on web servers get this much SMTP relay attempts?

Q: I don't use MailEnable to send email messages. I only use MailEnable for receiving email messages which are coming into the mail boxes that I've created for my domain name. Can I disable the whole SMTP server and still receive the incoming email messages? Or should I only disable SMTP relay? Will I still receive emails if I disable SMTP server relay? Or am I always required to turn on SMTP server relay in order to receive incoming email messages?

The SMTP service is the only way to receive any emails, as well as to send any emails. Disabling that service is the same as having no mail server at all.

It is very common for login attempts to be recorded in the SMTP logs, there are always people trying to gain access to active servers. These attempts are nothing to worry about, the problem will occur if they obtain the correct user name and password combination at which time they will be able to send spam through your server.